Import video for editing with multiple audio strips
This question has been asked before and there has been a Bug report which has been closed again, but it's been added to the ToDo list. 

So for now I'd suggest you'd use another tool* to extract your multiple tracks into individual files and import them all manually into the VSE.

* like Audacity with the ffmpeg plugin or VLC via its file saving mode, but that's offtopic here...